feat(server): add diagnostic logging for EGFX flow control and dispatch timing - #1834
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…ispatch timing The EGFX flow-control loop (backpressure, ack_suspended, FrameAcknowledge) and the server's per-PDU dispatch loop were both effectively invisible at default log levels. FrameAcknowledge, the single most important signal in the flow-control loop, was only logged at TRACE. Backpressure/ack_suspended transitions were not logged at all, and dispatch_pdu had no way to distinguish lock contention from a slow handler or runtime stall. - FrameTracker now edge-triggers a debug log when backpressure or ack_suspended change state, instead of logging every call (which would flood at 30+/sec) or nothing at all. - FrameAcknowledge is now logged at DEBUG with latency, queue_depth, and in-flight count. An ack for an unknown frame_id (protocol violation or stale ack per MS-RDPEGFX 2.2.4.3) is now a warning instead of silent. - drain_output (ZGFX compression) now tracks per-batch compress time and ratio, logging at INFO when a batch exceeds a 10ms budget and DEBUG otherwise, since it runs under both the state lock and the writer lock and can block inbound PDU processing. - Incoming EGFX DVC PDUs are logged at DEBUG with their kind, so the client-to-server side of the channel is visible without enabling TRACE. - dispatch_pdu and dispatch_events now separately time lock-acquisition wait and handler dispatch, warning when either exceeds 50ms so the two causes (lock contention vs. handler/runtime stall) can be told apart instead of both surfacing as one generic slow-dispatch symptom.
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I ran into a case where I needed to debug slow frame acknowledgement and dispatch stalls in ironrdp-server and ironrdp-egfx, and found the relevant signals were either missing or buried at TRACE level where nobody enables them in normal operation. This PR adds targeted diagnostic logging without changing any behavior.
No public API changes, no behavioral changes, logging only.
Note on CI: the workspace-wide test compile is currently broken on master independent of this PR, ironrdp-daemon's consume_output() call site passes a raw Receiver where OutputEventReceiver is expected. I confirmed this reproduces on a clean, unmodified checkout of master. This PR only touches ironrdp-server and ironrdp-egfx.